Underfeed stoker



4 Sheets-Sheet l g INVENTORI fiag rdm ATTORNEYS W. E. BIGGS UNDERFEED STOKER Filed April 30, 1928 April 18, 1933.

hp y f f A ril 18, 1933. w. E. BIGGS UNDERFEED STOKER Filed April 30, 1928 ,4; Sheets-Sheet 2 I ha INVENTOR flhu ATTORNEY A ril 18, 1933. WLE. BIGGS UNDERFEED STOKER Filed April 30, 1928 4 Sheets-Sheet '3 Invem ATTORNEYS April 18,1933. w. E. BIGGS 1,904,716

UNDERFEED STOKER Filed April so, 1928 '4 Sheets-Sheet 4 WHliHiHU ATTORNEYS Patented l8, 1933 UNITED STATES PATIENT orncs w"n.r.nm a. areas, or xxoxmm, 'rnnnnssnn mnarmm s'rolmn' Application filed April 80, 1928. Serial Hm 974,059

This invention relates to underfeed stokers for furnaces and has for its object to improve the grate construction in such furnaces, facilitate the feed of the fuel, and to- 5 in the aggregate form on each 81116 of the steam, in purpose 0 retort fuel supporting surfaces whose neral angle of inclination is downward in a lateral direction from the retort. The grate bars are especially constructed so "that in} dividual members can be readily removed, when burned or worn out, and replaced by new members without disturbing the construction of the furnace as a whole or the remaining portions of the grate surface. Furthermore, the invention includes an especially constructed upwardly inclined interior -end of the retort adjacent the end wall of the furnace, combined with means for injecting steam, preferably exhaust roximity to-the end wall for the f cooling the same and preventing the formation of clinkers thereon.

Preferably certain of the grate bars are constructed to reciprocate from and toward the retort, other members intermediate the reciprocating members being held in stationary position, and means are provided for reciprocating said movable members which means are actuated from the main source of power for feeding the fuel into the retort. This source of 4 wer may be any suitable mechanical or of ectric drive, steam a steam-actuated piston with a plunger head for feeding the fuel from a suitable hopper into the retort, while preferably connected to said plunger head is abar extending lontudinally of the bottom of the retort, hav mg attached thereto feeding abutments, as is usual in such constructions.

For the purpose of regulating the movements of the actuating piston, where a steam-actuated piston is employed, and of preventing the striking of said iston against the opposite ends of the ey 'nder within which it works, suitable means are provided for automatically controlling"fi ts movement by the exhaust steam from tlie cylinder.

The actuating piston for the pusher head has an intermittent reciprocating motionthat is, a forward stroke followed by a dwell, and a rearward stroke likewise followed by a dwell, and means are provided for effecting this intermittent motion' and producing the desired dwell. Preferably such means consist of a dashpot provided with a liquid, as oil which is permitted to have a regulated fl the dashpot to the other end, that is, to 0pposite sides of the dashpot piston. Other detailed features of the invention will be re-.

ferred to hereinafter. v

The invention is shown in the accompanyingflrawings in which v I igs. 1 and 1a together constitute a longitudinal, central sectional view through the furnace, the retort and .the actuating piston and its connections; a

Fig. 2 is a top plan view of the steam piston and its connections with the pilot valve mechanism shown in horizontal section;

Fig. 3 is a front elevation of the furnace with the air chamber or wind-box beneath the same; I

Fig. 4 is a central, transverse vertical section of the furnace; v

Fig. 5 is a view in perspective showing the connections for driving the grate bars and other moving parts;

Fig. 6 is a detailed perspective of a dumpor gas engine, etc., and as shown includes l Plate;

Fig. 7 is a like view of the retort end cap;

Fig. 8 is an expanded perspective'view showing the arrangement of the stationary and movable grate bars;

Fig. 9 is a broken detail of a portion of the retort; and

Fig. 10 is a plan view of a portion of the ow from one end of the fuel bed to support combustion. The

through the furnace, pre

of air under pressure from the chamber 1 to,

the chambers 2 or 2 as the case may be,

maybe effectively controlled. Immediategy above the air chamber 1 is a retort 4 exten ing from the front of the furnace to the rear wall 5. Preferably this retort is inthe form of a long trough or channel, U-shaped in cross section as shown in Fig; 4, and at its upper edges terminates iii-laterally extendin flanges 4'. The wind-box 1 opens upwar ly into the space 6, Fig. 4, extending-the full length of the retort 4 and lat erally approximately to the outer limits of the fuel supporting surface, as'will be readily understood from aninspection of Fig. 4. On either side of the retort two longitudinally extending sup orts 7, 7', extend ihrably in the form of angle bars, which bars form the su ports for the outer ends of the grate bars, t e inner ends of which rest upon the flanges 4 of the .,retort. These flanges' of the retort are provided with downwardly extending lugs 4", see Fig. 9, which lugs are suitably spaced for a purpose hereinafter to be described.

The construction of the grate bars will be best understood from an inspection of Figs. 4, 5, 8 and 10. As here shown, three of the grate bars are secured together so as to form a single unit and are so mounted as to remain stationary, while a.movable bar is mounted between compound units of stationary bars and is arranged to be reciprocated longitudinally of the bar for the purposeof moving the fuel laterally to either side from the retort. Referring to Fig. 8, the three stationary grate bars 8, 8' and 8" are provided with an upwardly extending portion forniing approximately a continuation of the walls of the retort 4 and with laterally'and downwardly inclined ortions extending out to the supporting ars 7 Each of these grate bars 8, 8 and 8" .has one .plane side surface, and the other side is provided with a series of ribs 9, 9 and 9", the. several ribs being spaced apart to form air passages for the supply of air to ribs 9 are inclined outwardly and upwardly from the retort. The ribs 9' are approximately vertical, while the ribs 9" are also inclined outwardly and upwardly but at a. very small angle. Moreover the air passages between the ribs 9 are deeper than the air passages between the ribs 9' and the air passages between the ribs 9", to the end eeann;

that the amount of air supplied to the fuel bed will be greater in that portion of the grate bar adjacent the retort, and will grad: ually decrease in cross sect1on,and conse quently in the amount of air supplied to the fuel, outwardly towards the outer ends of the grate bars. All of the grate bars 8, 8

and 8" are provided with downwardly extending webs 10, and the lower inner ends of these webs 10 on the grate bars Sand 8 are provided with lugs 10. These three bars 8, 8 and 8" are assembled in the man- Fig. 8, there is provided a series of air channels 12 between the bars.

The movable bar 13, Fig. 8, is'provided with ribsv exactly similar in arrangement, spacing, etc, as has just been described in connection with the ribs on the stationary bars 8, 8' and 8". The bar 13 is provided with a central downwardly extending web 14 from which web there extends a lug 15 forward toward the retort. Thit web 14 has cut therein an inverted U-shaped opening 16 for a purpose hereinafter to be described.

Referring now to Figs. 8 and 10, it will be seen that the outer ends of the webs on the bars -8 and 8" are somewhat shorter than the outer end of the web 11 the bar 8, and when these three bars are olted together they are placed in osition by inserting the 10, 10' under the flange 4 of the'retort 111i 4 tween the lugs 4" on said flange, and then dropping the outer ends of the three bars thus secured together onto the upper surface of the bars 7, 7 the ends of the webs 10 of the bars 8 and 8" coming against the inner edges of the flanges on the bars 7 and 7 while the outer end of the web on the bar 8, which as above'indicated is slightlyv longer than the other webs, drops through ,a notch 17 Fig. 10, formed in the flange movement of the outer end, and by the lugs 10' engaged 'betweenthe lugs 4 at the inner end. The bars cannot be lifted at the inner ends because the lugs 10' are engaged under the flange 4'. Nevertheless the group of bars can be quickly and readily removed by raising the outer end until the webs theret of clear the flanges on the bars 7, 7'. The

web 14 on the movable bar 13 terminates at outer end so as to leave an intervenlng space between the end-of the web and the supporting angle bars 7, 7 to the bustion of any of the unconsumed fuel that may reach said dump plates. The air for supporting combustion on these dump plates is admitted from the chamber 6 through the dampers 3, 3' to the chambers 2, 2' as will be readily understood from an inspection of Fig. 4.

For the purpose of supplying fuel to and feeding the same through the retort in the furnace, there is provided the usual or any suitable hopper 20 in which the fuel is placed, which hopper opens into the outer end of the retort as shown in Fig. 1. Fuel is fed from the hopper 20 to the retort by means of a suitable reciprocating plunger actuatedby any suitable source of power. In the form shown, the plunger is operated by a steam engine, and to thls end a steam cylinder 21 is suitably supported in front of the hopper, in which cylinder plays a piston 22 whose piston rod 23 extends toward the retort and has on its end a plunger 24. The fuel is fed from the bottom of the hopper 20 in front of the plunger 24 and by said plunger is forced forward into the retort, and a push bar 23' is secured to the plunger and extends along the bottom of the retort, as will be readily understood and as is usual in this art. This bar'is provided with suitably spaced feed blocks or shoulders 23" for advancing the fuel through the retort.v

The construction of this plunger and associated parts is preferabl such that the plunger head or pushing ace may be removed and replaced in case of wear, especially between the upper edge thereof and the lower edge of the hopper 20-where the plunger passes into the retort. Referring now to-Figs. 1 and 5, the plunger 24 comprises a hollow cylindrical casing threaded at its rear or outer end on a cross-head 25 which is loose on the piston rod 23 and normally abuts against a shoulder 25 formed thereon. At the other end of the plunger, .a head or plate 91 has a portion 92 of reduced diameter fitting within the end of the plunger casing andis held from turning relatively thereto by a pin) or pins 93. The end of the piston rod 23 passes through the head 91, and nuts 94 on the end of sand rod serve to clamp the assembly of cross-head casing and p 'ver 35, move upward together.

nger head J rigidly together against the shoulder 25'. To permit of ready attachment to or removal from theplunger of the push bar 23', the piston rod 23 passes loosely through 'a supporting member 95, which is clamped against the head 91 by the nuts 94 and is prevented from turning relatively to the latter by a pin or pins 96. The member 95 has a projectin boss 97 which is provided with a 'tappe threaded opening 98 to receive the threaded end of the push bar 23'. Should it be desired to remove or replace the push bar or plunger head, it is only necessary to remove the nuts 94, when said members may be freely disengaged.

The cross-head 25 has pivoted t0.its outer ends two links 26, 27, extending forward and connected respectively to the long arms, 28 and 29, of two bell-crank levers fulcrumed on a'suitably supported bearing 30, said levershaving their short arms 31 and 32 extending forward where they are pivotally connected to two vertical rods 33 and arms 39, and a rod 42 is mounted in the upper ends of'the arms 40. These rods 41 and 42 extend through and. engage in the U- shaped grooves 16 of the webs of the mov-- able bars 13, as will be understood from an inspection of Fig. 4.

Fixedon the forward shafts 37 and 38 are two housings 43 and 44, into which housings the levers 35 and 36, pivoted onv such rock shafts, extend, and

within which said levers are free to move within limits which are determined by suitends of the rock able abutments in the form of screws 45, 46.

The lever 35, for example, can move upward without moving the rock shaft 37 until it contacts with the screw 45, after which the housing 43 on the rock shaft 37 and the leverse or downward movement of the'lever 35 said lever moves without rocking the shaft 37 until it contacts with the lower screw 45, after which the shaft moves with On the reand is rocked by the lever 35. The same 7 action of the parts is true in connection with the shaft 38 and the lever 36.

As the piston rod 23 moves inward it will in a direction to move the movable grate bars 13 inward. On the other hand, when the piston rod 33 is moved outward, that impart a downward thrust to the links 33 v a and 34, and will rock the shafts 37 and 38.

- ably supported on or any suitable ex is from right to left in Fi 5, the links 33 and 34 will have an upwar thrust imparted thereto, and the shafts 37 and 38 will be rocked so as to movethe rods 41 and 42 outward and with them the movable grate bars 13. The result of this will be an outward movement of the movable bars of the grate on either side, and then an inward movement of said bars, with the result that the fuel bed will be moved outward.

Steam is admitted to the cylinder 21 through an inlet pipe'50 controlled by a suitable slide valve 51. The position of this slide valve 51 is controlled by a rod 52 carrying pistons 53, 54 at the ends thereof, which istons are reciprocated in cylinders 55, 56 by steam admitted to said cylinders through steam channels 57, 58, Fig. 2, which channelsare controlled, in turn, by-a slide valve 59 attached to a rod 60. This rod 60 has adjustable stops 61 and 62 thereon, between which plays a sliding sleeve 63, conuected by a link 64 to a lever 65 keyed on a shaft 66 mounted to turn'in bearings suitstocker. This shaft 66 has a downwardly extending lever 67 slotted at itslower end, as' at 68, and en aging a stud 69 extending outward from t e cross-head 25. The reciprocation of the cross-head 25 rocks the lever 67 backward and forward and this imparts a backward and forward thrust to the rod 60, thereby shifting the valve 59 so-as to uncover first one and then the other of the steam passa es 57 and 58. The usual Tlaust ports are provided in the respective cylinders 55 and 56.

The movements of the are controlled by a dash ot consisting of a cylinder 70, within whic plays a piston 71 connected by a rod 72 to the pistons 53 and 54. Any suitable liquid, as oil, is supplied to the cylinder on the opposite's'ides of the piston 71 from a suitably elevated reservoir 72, Fig. 1, from which extends a pipe 73 which, preferably adjacent to cylinder 7 O, is provided with two branches 74 and 75, one extendin to either side of the piston 71 into the cy inder 70. Check valves 76. and 77 are provided in the branches 74 and 75, which branches are connected by a bypass 78 provided with va suitable valve, as a needle valve 79, which valve is either manually manipulated or can be connected to a suitable damper regulator through the lever 80 and the cable 81,

Exhaust steam is led out from the cylin:

'der 21 through the exhaust pipe 82, by means of the usual admission and exhaust passages 83 and 84 and the slide valve 51. Since the slide valve 51 has a retarded action, the piston 23 is likely to slap against the end of the cylinder at the end of its stroke before the valve 51 has been reversed to admit steam behind the piston. To prevent this, suitable the framework of the pistons 53 and 54.

cushioning means are provided, which in the embodiment shown are applied only to the outward stroke of the iston since the resistance opposed by the i iiel is suflicient for this urpose on its inward stroke. As shown, t e admission and exhaust port of passage 83 at the outer end of the cylinder 1s spaced from the end of the latter and is covered by the piston 23 before it reaches the end of the outward stroke. This prevents further exhaustthrou h passage 83, and' forms a compression c amber which acts as a cushion, in which sufiicient pressure is created to start the return stroke of the piston as soon as slide valve 51 has opened passage 84 to the exhaust pipe 82. The initial return stroke of the piston caused by this pressure can readily be madesufiicient to-uncover the port of passage 83 and admit live steam behind the piston.

As the piston moves in one direction in the cylinder 21, it acts to shift the pilot valve 59 so as to admit steam behind one of the pistons 55, 56, which pistons are moved over slowly. As the dashpot piston moves therewith, the rate of movement is determined b the setting of the-needle valve 79. When t e pistons 55 and 56, as the case may be, have shifted the slide valve 51, the reverse action takes place, but it will be observed that there is necessarily a dwell in the reciprocations of the piston 22, depending upon the time necessary for the piston 71 in the dashpot to pass the oil from one side of the piston 71 through the needle valve 7 9to the other side sufliciently to permit the slide valve 51 to be moved into the reverse position. l

The, exhaust pipe 82 is led into" the furnace along one side of the retort to its extreme inner end, and then across and under the upwardly inclined end thereof adjacent to and thusserve also to cool the wall above the retort. I

For the purpose of providing an eflicient and yet readily removable cap to the upwardly inclined end of the retort, the construction shown in Figs. 1a and 7 is provided, suchconstruction taking the form of a cap 85. This capis preferably in the form of a casting having lugs 86 on the lower portion thereof which engage under a flange 87 on the upwardly inclined portion of the retort, and also has a downwardly extending flange 89 abutting the wall 5 of the furnace,

This cap is provided with ports or openings .90 for, the passage of steam upward therethrough. The steam escaping from the pipe 82 serves to keep the cap, the wall above the cap and the wall below the cap, cool.

" the inclined end of the retort, these parts,

. which are liable to become burned out in use, may be readily removed as individual elements, either for repair or re lacement by 'new parts, and this without isturbing the construction of the furnace or the ate as a whole. Moreover, these individual grate bars, as well as the compound grate bar unit and the inclined cap constitute in and of themselves structures capable of manufacture separate from the manufacture of the furnace as a whole, but of which they constitute elements in combination, and such elements are therefore hereinafter claimed per se.

'It will furthermore be appreciated that the means for cushioning the stroke of the ower piston is one of exceedingly simple esign and the same is true of the design and con-.

struction of the means for supplying the dashpot structure of the slide valve with fluid and regulating the rate of passage of said fluid from one side to the other of the piston of the dashpot.

While the invention as a whole has been described herein with considerable detail,

it will of course be understood by those skilled in the art that variations can be made within the s irit of the claims hereto tort flanges, lugs on said grate bars engag-.

ing the under sides of sald flanges,- means supportin the outer ends of said grate bars, downwar 1y extendin shoulders on said grate bars opposite sa d supporting means, and means restraining said grate bars against movement longitudinally of the retort, whereby the grate bars are maintained in spaced relation and restrained against vertical movement at the ends thereof adjacent the retort.

2. In an underfeed stoker, the combination of -a' retort having laterally extending to flanges, and means feeding fuel along said retort, with'a grate comprising a plu rality of grate bars forming a stationary unit whose retort end is supported 'by said retort flange and a grate bar movable transversely of the retort and whose retort end is supported by said flan e, means restraining the inner ends of sai unit and movable grate bar against vertical movement, lugs on said unit and said movable bar engaging the under side of said flange, means supporting the outer, ends of said unit and said "movable'bar, a downwardly extending shoulder on said unit engagin said supporting means and restraining t e said unit against movement transverse to the retort,

means reciprocating said movable bar trans-y grooved and one plane side face, means restraining the inner or retort ends of said bars from vertical movement, means restraining a plurality of said bars from movement transverse to the retort and from movement longitudinally thereof, trans-' versely extending movable bars interposed between said last named bars, and means imparting movement to said movable bars, transverse to said retort.

4. In an underfeed stoker, the combination of a retort, means feeding fuel alon the same, and an air chamber beneath sai retort, with a grate having bars extendin transversely of the retort the retort ends 0 which bars are "supported by said retort,

means supporting the outer ends of said bars, said grate comprising stationary comound units alternating with single movale bars, means reciprocating said movable.

bars transversely of the retort, and means restrainin the retort ends of said units and said bars. rom vertical and from movement,

longitudinally of the retort.

5. In an underfeed stoker, the combination of a retort and means for feedingfuel thereto, of a series of grate bars on each side of the retort andextending outwardly therefrom, each of said bars having a first portion extending upward and slightly outward from the retort, a second portion ex-' tending outward and slightl downward from said first portion, a thir portion extending. outward and shar ly downward from saids'econd portion an a. fourth portion sloping Outward and gently downward' from the third portion, said second portion having approximately vertical air conducting grooves formed in one face of the bars and another. portion having approximately [horizontal grooves formed in said face.

6. In an underfeed stoker, the combination of aretort and plunger means for feeding fuel thereto of two series of grate bars, one on either side of said retort, means restraining the inner or retort ends of said bars from vertical movement, means restrainingsaid bars from movement longitudinally of the retort, and means supporting the outer ends of said bars while leaving said ends free for upward'movement.

7.111 on nnolerfeed Stoker, a combination of a retort, a, fuel ush bar, apower actuated plunger rod, a ollow pl I" mounted 'thereon, a removable plunger ace mounted 5 oil-said plunger rod and closing the forward end of the plunger and means connecting aid push bar to saifi removable plunger nee.

V In testimony whereof I have signed. this in specification.

' Ev BIGGS. 

